Andrea Natale

Provocation of Hypotension During Head-Up Tilt Testing in Subjects With No History of Syncope or Presyncope

BACKGROUNDnHead-up tilt test is increasingly being used to evaluate patients with syncope. This study was designed to evaluate the specificity of head-up tilt testing using different tilt angles and isoproterenol infusion doses in normal volunteers with no prior history of syncope or presyncope.nnnMETHODS AND RESULTSnOne hundred fifty volunteers were randomized to two groups of 75 each. In group 1, subjects were further randomized to have head-up tilt testing at a 60, 70, or 80 degree angle at baseline followed by repeat tilt testing during a low-dose isoproterenol infusion that increased the heart rate by an average of 20%. In group 2, after having a baseline head-up tilt test at a 70 degree angle for a maximum of 20 minutes, subjects were randomized to have a repeat tilt table testing at a 70 degree angle during a low-dose, 3 micrograms/min, or 5 micrograms/min isoproterenol infusion. In group 1, syncope or presyncope along with hypotension developed in 2 subjects during the baseline test at 60 and 70 degrees of tilt and in 5 subjects during tilting at 80 degrees. The addition of low-dose isoproterenol reduced the specificity minimally from 92% to 88% at both 60 and 70 degrees of tilt but substantially to 60% at an 80 degrees angle. However, 6 of the 10 subjects with a positive test at an 80 degree angle had an abnormal response after 10 minutes of tilt testing. In group 2, using various isoproterenol doses with tilt table testing at a 70 degree angle, low-dose (mean infusion dose, 1.5 +/- 0.45 microgram/min), 3 micrograms/min, and 5 micrograms/min isoproterenol infusions elicited an abnormal response in 1 (4%), 5 (20%), and 14 (56%) of the subjects, respectively. Using multiple logistic regression analysis, head-up tilt testing at an 80 degree angle (P = .01) or during 3 micrograms/min (P = .02) and 5 micrograms/min isoproterenol infusion rates (P < .001) was the most significant predictor of an abnormal response.nnnCONCLUSIONSnHead-up tilt testing at a 60 or 70 degree angle with or without low-dose isoproterenol infusion provides an adequate specificity. Caution is needed, however, in interpreting the results if the head-up tilt test at 80 degrees is extended beyond 10 minutes or if high doses of isoproterenol are used.

Sustained Ventricular Arrhythmias in Patients Receiving Thrombolytic Therapy Incidence and Outcomes

BACKGROUNDnSustained ventricular tachycardia (VT) and fibrillation (VF) occur in up to 20% of patients with acute myocardial infarction (MI) and have been associated with a poor prognosis. The relationships among the type of arrhythmia (VT versus VF or both), time of VT/VF occurrence, use of thrombolytic agents, and eventual outcome are unclear.nnnMETHODS AND RESULTSnIn the GUSTO-I study, we examined variables associated with the occurrence of VT/VF and its impact on mortality. Of the 40 895 patients with ventricular arrhythmia data, 4188 (10.2%) had sustained VT, VF, or both. Older age, systemic hypertension, previous MI, Killip class, anterior infarct, and depressed ejection fraction were associated with a higher risk of sustained VT and VF (P<0.001). In-hospital and 30-day mortality rates were higher among patients with sustained VT/VF than among patients without sustained ventricular arrhythmias (P<0.001). Both early (<2 days) and late (>2 days) occurrences of sustained VT and VF were associated with a higher risk of later mortality (P<0. 001). In addition, patients with both VT and VF had worse outcomes than those with either VT or VF alone (P<0.001). Among patients who survived hospitalization, no significant difference was found in 30-day mortality between the VT/VF and no VT/VF groups. However, after 1 year, the mortality rate was significantly higher in the VT alone and VT/VF groups (P<0.0001).nnnCONCLUSIONSnDespite the use of thrombolytic therapy, both early and late occurrences of sustained VT or VF continue to have a negative impact on patient outcome; patients with both VT and VF had the worst outcome; and among patients who survived hospitalization, the 1-year mortality rate was significantly higher in those who experienced VT alone or VT and VF.

Circulatory and catecholamine changes during head-up tilt testing in neurocardiogenic (vasovagal) syncope.

Changes in heart rate, arterial pressure, norepinephrine and epinephrine levels were compared in 19 consecutive patients (10 men and 9 women, mean age 46 +/- 16 years) with neurocardiogenic syncope and 11 age- and sex-matched control subjects (5 men and 6 women, mean age 49 +/- 15 years) during head-up tilt testing. Norepinephrine and epinephrine levels were measured at the baseline supine position, in the initial upright position, every 90 seconds during the 70 degrees upright tilt, at the time of termination due to hypotension and syncope (or at 15 minutes in control subjects), and at 40 seconds and 1 minute and 40 seconds in the supine position after terminating the head-up tilt test. Baseline norepinephrine, epinephrine and heart rate were slightly higher in patients. Despite a significant decrease in mean arterial pressure during head-up tilt testing in patients (51 +/- 20 mm Hg; p < 0.001), norepinephrine levels in patients and control subjects at the time of terminating the head-up tilt test were comparable (459 +/- 204 vs 473 +/- 172 pg/ml). A fivefold increase in epinephrine levels (73 +/- 53 to 345 +/- 260 pg/ml; p < 0.01) were seen in patients, whereas control subjects had insignificant change (38 +/- 16 to 65 +/- 44 pg/ml). It is concluded that diminished neuronal sympathetic activity and enhanced adrenomedullary activity is demonstrated during head-up tilt testing in patients with neurocardiogenic syncope.

Impact on ventricular function and quality of life of transcatheter ablation of the atrioventricular junction in chronic atrial fibrillation with a normal ventricular response

We assessed left ventricular function and quality of life after atrioventricular junction ablation and pacemaker implant in 14 patients with chronic atrial fibrillation and normal ventricular response. A significant improvement in left ventricular ejection fraction, fractional shortening, and functional capacity were observed at follow-up, suggesting that in patients with chronic atrial fibrillation a regular heart beat may be preferable over rate control.

Efficacy of Different Treatment Strategies for Neurocardiogenic Syncope

Objectives: The purpose of this study was to evaluate the efficacy of different therapeutic approaches for patients with a history of syncope and positive head‐up tilt testing. Background: Head‐up tilt testing has gained broad acceptance as a reliable diagnostic method for the assessment of patients with recurrent unexplained syncope. However, once the diagnosis is established, there is no consensus on the most appropriate treatment. In this respect, efficacy of drug therapy in preventing recurrence of symptoms in such patients is not entirely clear, and controversies exist regarding the need to confirm the effects of pharmacological interventions. Methods: Clinical follow‐up was obtained in 303 patients with a history of syncope and positive head‐up tilt testing. After the diagnostic head‐up tilt, patients were assigned to different therapeutic approaches according to their preference or logistic impediments. Of 303 patients, 44 received empiric therapy, 210 were treated with medications proven effective during repeated head‐up tilt testing, and 49 refused or discontinued medical therapy. The three groups were similar with regard to age, sex, and clinical presentation. The mean follow‐up was 2.8 ±1.8 years. Among the patients treated according to head‐up tilt guided therapy, 130 were on beta blockers, 35 on theophylline, 10 on ephedrine, 31 on disopyramide, and 4 on miscellaneous regimens. Empiric treatment consisted of beta blockers in 37 of 44 patients and other drugs in the remaining patients. Results: During the follow‐up, recurrence of symptoms was experienced in 12 (6%) of the 210 patients receiving the head‐up tilt guided therapy, 16 (36%) of 44 in the empiric therapy group, and 33 (67%) of 49 in the no therapy group. Recurrence of symptoms in patients on empiric or no therapy was significantly more frequent as compared to the head‐up tilt guided therapy group (P<0.01). Conclusions: In patients with unexplained syncope and positive upright tilt testing, therapeutic strategies identified on the basis of response during head‐up tilt have a more positive impact on the recurrence of symptoms during follow‐up.

Testing different biphasic waveforms and capacitances: Effect on atrial defibrillation threshold and pain perception

OBJECTIVESnThe goal of this study was to compare the effect of different tilts and capacitances for biphasic shocks on atrial defibrillation efficacy and pain threshold.nnnBACKGROUNDnAlthough biphasic shocks have been shown to be superior to monophasic shocks, the effect of tilt and capacitance on atrial defibrillation success and pain perception has not been studied in patients.nnnMETHODSnAtrial defibrillation threshold (DFT) testing was performed using a right atrial appendage/coronary sinus lead configuration in 38 patients with a history of paroxysmal atrial fibrillation undergoing an invasive electrophysiologic study. Biphasic waveforms with 40%, 50%, 65%, 80%, 30%/50% and 40%/50% were tested randomly in 22 patients (Group 1). In 16 patients (Group 2), a 65% tilt waveform with 50- and 120-microF capacitance was tested. Before sedation, pain sensation was graded by 15 patients in Group 1 after delivery of a 0.5-J shock and by 10 patients in Group 2 after two 1.5-J shocks with 50- and 120-microF capacitance were delivered.nnnRESULTSnThe DFT energy for the 50% tilt waveform was significantly lower than the 65%, 80% and 30%/50% tilt waveforms. The 40%/50% tilt waveform provided slightly lower energy requirements than the 50% tilt waveform. Nine patients (60%) described the 0.5-J shock as very painful, and four (26.6%) complained of slight pain. The 50-microF capacitor lowered energy requirements compared with the 120-microF capacitor. Six patients (60%) perceived the 1.5-J 50-microF capacitor shock as more painful, whereas three (30%) perceived both shocks as equally painful.nnnCONCLUSIONSnBiphasic waveforms with 50% tilt in both phases and a smaller tilt in the positive phase than that in the negative phase (40%/50%) provided a decrease in energy requirements at atrial DFT. In addition, stored energy was reduced by biphasic shocks with 50-microF capacitance compared with 120-microF capacitance. Despite the reduction in energy requirements, shocks < 1 J continued to be perceived as painful in the majority of patients.

Relevance of asystole during head-up tilt testing

The prognosis of patients manifesting prolonged asystole during head-up tilt testing is unclear. In 209 consecutive patients with a history of syncope and positive head-up tilt tests, 19 had asystole lasting > 5 seconds (mean duration 15 +/- 10) (group 1a). When compared with patients without asystole (group 1b), group 1a patients were younger (32 +/- 12 vs 47 +/- 21 years, p < 0.005), but clinical manifestations were not any more dramatic (the number of episodes of syncope [7 +/- 5 vs 8 +/- 6 episodes, p = NS] and injury during syncope [2 vs 13 patients, p = NS] were similar). During follow-up (mean 2 +/- 1 year), with the patient taking pharmacologic therapy such as beta blockers, ephedrine, theophylline, or disopyramide, the recurrence rate was 11% and 8% in groups 1a and 1b (p = NS). No patient in the asystole group underwent pacemaker implantation. Additionally, of 75 normal volunteers (group 2) with no history of syncope undergoing tilt tests to define its specificity, 3 had asystole (mean duration 10 seconds). During > 1 year of follow-up, despite no treatment, all 3 are symptom free. Thus, asystole during head-up tilt testing does not predict either a more malignant outcome or a poor response to pharmacologic therapy. Moreover, an asystolic response does not enhance the specificity of the head-up tilt test because it may be present in asymptomatic normal volunteers.

Ventricular fibrillation and polymorphic ventricular tachycardia with critical coronary artery stenosis: does bypass surgery suffice?

ICD Therapy and CABG for Sudden Death. Introduction: Previous studies have suggested that coronary artery bypass surgery is sufficient to prevent recurrence of sudden death in patients with critical coronary artery stenosis presenting with ventricular fibrillation or polymorphic ventricular tachycardia. We present our experience in patients with one or more episodes of sudden death associated with documented ventricular fibrillation or polymorphic ventricular tachycardia and severe operable coronary artery disease who underwent defibrillator implant at the time of bypass surgery.

Prospective Evaluation of New and Old Criteria to Discriminate Between Supraventricular and Ventricular Tachycardia in Implantable Defibrillators

This study was designed to evaluate the ability to distinguish between supraventricular tachycardias (SVTs) and ventricular tachycardias (VTs) based on onset, stability, and width criteria in an implantable defibrillator. Inappropriate detection of atrial fibrillation and sinus tachycardia is a common problem in patients with implantable defibrillators. The onset, stability, and width criteria were studied in 17 patients who underwent implantation of a Medtronic 7218C implantable defibrillator by inducing sinus tachycardia and atrial fibrillation. Additional data on the width criteria was obtained by pacing at separate sites in both the left and right ventricle. Patients were studied at different times for up to 6 months to determine any changes in the criteria. The onset and stability criteria caused inappropriate detections in 36% and 12% of the episodes, respectively. The addition of the width criteria decreased the inappropriate detection using the onset and stability criteria to 5% and 2%, respectively. Pacing from the RV apex, RV outflow tract, and LV apex was appropriately detected as wide in 76%, 41%, and 94%, respectively. The width criteria changed over time in individual patients, but was stable by 6 months in all but one patient. No single criterion is satisfactory for distinguishing between SVT and VT in this patient population, but the combination of criteria seems to provide better discrimination. The width criteria can change dramatically over time and needs to be monitored carefully. Newer algorithms will need to be developed to allow better detection of supraventricular tachycardias.

Preliminary experience with a hybrid nonthoracotomy defibrillating system that includes a biphasic device: Comparison with a standard monophasic device using the same lead system

OBJECTIVESnThis study analyzed the advantage of combining a biphasic device with a transvenous system and compared the results with those obtained with a standard monophasic device.nnnBACKGROUNDnAvailable lead systems use monophasic pulses and may require lengthy intraoperative testing to achieve adequate defibrillation threshold in a conspicuous number of patients. The option of biphasic waveform may provide further benefits. However, clinical experience with a permanent implant is lacking.nnnMETHODSnFifty-five patients underwent testing and received a permanent implant using the Endotak lead system associated with a CPI monophasic device. The remaining 36 patients received a permanent implant with the Endotak lead system connected to a biphasic device. In both groups a subcutaneous patch was combined when needed to obtain acceptable defibrillation thresholds.nnnRESULTSnBiphasic pulses resulted in lower mean (+/- SD) defibrillation thresholds (monophasic 15 +/- 4.7 J vs. biphasic 12 +/- 5 J, p = 0.03) and a better implantation rate (100% biphasic vs. 89% monophasic, p = 0.07). Biphasic pulses allowed implantation with less ventricular fibrillation induction (7.4 +/- 3.2 vs. 3.5 +/- 1.8, p < 0.01) and a mean shorter procedure time (168 +/- 39 vs. 111 +/- 30 min, p < 0.01). With the biphasic waveform a greater proportion of patients met the implantation criteria with the lead system alone (83% vs. 45%, p < 0.01). When needed, the left prepectoral location of the patch electrode was always sufficient in left subscapular position was required in 15 patients in the monophasic group. Implantation of the biphasic device was associated with a shorter mean hospital stay (3.8 +/- 0.8 vs. 5.4 +/- 2.2 days, p < 0.01).nnnCONCLUSIONSnIncorporation of a biphasic device in a transvenous implantable cardioverter-defibrillator uniformly increases the efficacy of the system and the ease of implantation.